1. Field
The present invention relates to a printed circuit board comprising a metal bump and a method of manufacturing the same, and, more particularly, to a printed circuit board comprising metal bumps, the metal bumps having constant diameters and arranged at fine pitches, and a method of manufacturing the same.
2. Description of the Related Art
With the advancement of electronics industry, electronic parts have become highly functionalized, and thus a package (PKG) is required to be miniaturized and highly-densified. Further, an interposer (substrate) for connecting an IC to a main board is also required to be highly-densified. The densification of the package is caused by the increase in the number of I/Os, and methods of connecting the package with the interposer have improved. Currently, as a method of mounting an IC in a high-density package, a wire bonding method and a flip bonding method are used. Among them, the flip bonding method may be used due to the costs required to mount the IC when the number of I/Os is increased.
FIG. 1 is of sectional views showing a conventional process of manufacturing a substrate on which a semiconductor chip is mounted.
First, as shown in FIG. 1A, a carrier 1 formed of a double-sided copper clad laminate is provided, and then, as shown in FIG. 1B, a solder resist 3 is applied on the carrier 1, and then, as shown in FIG. 1C, a dry film 5 is applied on the solder resist 3 and then patterned. Thereafter, as shown in FIG. 1D, electrolytic plating is conducted, and then, as shown in FIG. 1E, the dry film 5 is removed to form connection pads 7. Subsequently, as shown in FIG. 1F, a first insulation layer 9 is formed on the connection pads 7 and the solder resist 3, and then, as shown in FIG. 1G, a first circuit layer 11 is formed.
Thereafter, as shown in FIG. 1H, a build-up layer 13 is additionally formed by repeating the above processes, and then, as shown in FIG. 1I, a solder resist 15 is applied on the build-up layer 13.
Subsequently, as shown in FIG. 1J, the carrier 1 is separated by conducting a routing process, and then, as shown in FIG. 1K, copper foil is etched and removed. Then, as shown in FIG. 1L, the solder resists 3 and 15 are patterned to form openings 17 for exposing the connection pads 7.
Thereafter, as shown in FIG. 1M, solder balls 19 for flip chip bonding are formed in the openings 17. The formation of the solder balls 9 is conducted through a solder paste printing process using screen printing and a reflow process.
However, as described above, the method of forming a bump on a printed circuit board using a printing process is problematic in that large connection pads are required, and thus it is difficult to realize bump arranged at fine pitches of 120 μm or less.
Further, the method of forming a bump on a printed circuit board using a printing process is problematic in that a fine bump is not formed, or its volume is very small even though the fine bump is formed.
Further, in the method, since the connection pads are formed by plating, their thicknesses are different from each other due to plating deviation, and, since solder paste cannot be easily printed in a completely uniform manner even in the solder paste printing process, the heights of solder balls are not uniform, so that there is a problem in that solder balls which are not connected to a semiconductor chip are formed.
Further, in the method, since the stepped portion of the solder resist 15 is large, there is a problem in that voids are formed in an underfill process performed after the mounting of an electronic part.